326 E. M. KINDLE — ^RECONNAISSANCE OF PORCUPINE VALLEY 



The upper limit of tlie Silurian series was not observed in the Lower 

 Ramparts. It was recognized, however, 1 mile above the mouth of Sal- 

 montrout river, where Devonian limestones overlie the Silurian. This 

 highest bed of the Silurian series consists of fissile black shale and inter- 

 bedded dark siliceous limestone. Xot more than 30 feet of these beds are 

 exposed. Two or three species of graptolites abound in the shale. 



This fauna, which is of somewhat later age than the fauna just de- 

 scribed, occurs in a black shale at the base of the Devonian section. It 

 was found 1 mile above the Indian village, at Old Eampart House, on 

 the east bank of the Porcupine river. The shale, which is about 25 feet 

 thick, contains some thin bands of black siliceous limestone. About 325 

 feet of Devonian limestone follows the shale in the section. Graptolites 

 occur in one or two beds of the shale in abundance. Associated with 

 them are a very few brachiopods. This graptolite fauna was referred to 

 Mr E. 0. Ulrich, who finds the state of preservation not perfect enough 

 to permit of specific determination. He considers the fauna of "either 

 late Magaran or Cayugan" age, and reports the following faunal asso- 

 ciation : 



Silurian Fauna, tipper Ramparts 



Monograptus sp. undet. 



Cyrtograptus sp. undet. 



OrMculoidea. 



? Gamarotoechia. 



? Uncinulus. 



1 Sieier-ella (a small species of pen- 



tameroid shell possibly of this 



genus). 



1 Rafinisquina (a very small concen- 

 trically wrinkled specie^). 

 ? TJneinuliis. 

 Spirifer of. radiatus. 

 Dalmanella. 



Graptolites have been found at but one other locality in Alaska. In 

 the Mount McKinley region Brooks and Prindle* found graptolites which 

 Schuchert referred to three species : 



Glimacograptus iicornus Hall. 

 Climacograptus sp. undet. 



Decranograptus cf. ramosus (Hall). 



These represent a fauna much older than the Old Eampart graptolites 

 which Schuchert considered to mark a horizon about equivalent to the 

 Utica of the Ordovieian. 



Graptolites have been reported from only two localities in the western 

 part of the Dominion of Canada. Both of these are in British Columbia. 

 Neither of the genera found in the Old Eampart fauna is present in the 



* An exploration in the Mount McKinley region. 

 Survey, 190G. (In preparation.) 



Bulletin of tlae TJ. S. Geological 



